Apparatus and method for filtering well fluids

ABSTRACT

Apparatus and method for filtering well fluids standing in the casing of a well borehole by extending a screen filter down the well borehole, the filter having apertures therein of a sufficient size to pass well fluids therethrough while excluding particles of a predetermined size. The filter is closed at the top and open at the bottom and is extended into contact with the well fluids thus forcing the fluids up through the filter and out into the well borehole above the filter while trapping the particles therein.

ilite States Patent 1 1 Burnside 1 May I, 1973 [541 APPARATUS AND METHOD FOR 2,550,080 4/1951 Moore ..166 99 FILTERING WELL FLUIDS 3,058,525 10/1962 Humphries 166/1 77 Us. (:1 "166/177, 166/31 1 rm. c1 ..E2lb 21/00, E2lb 37/02 Field of Search 166/31 1, 99, 177,

References Cited UNITED STATES PATENTS 10/1961 Orr. ..l66/3llX 3/1970 Burbaetal. ..l66/3ll Primary Examiner-David H. Brown Attorney-l-larold L. Denkler and Theodore E. Bieber [57] ABSTRACT Apparatus and method for filtering well fluids standing in the casing of a well borehole by extending a screen filter down the well borehole, the filter having apertures therein of a sufficient size to pass well fluids therethrough while excluding particles of a predetermined size. The filter is closed at the top and open at the bottom and is extended into contact with the well fluids thus forcing the fluids up through the filter and out into the well borehole above the filter while trapping the particles therein.

7 Claims, 5 Drawing Figures Patented May 1, 1973 3,730,268

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' INVENTOR.

FLOYD D. BURNSIDE Patented May 1, 1973 3,730,268

2 Sheets-Sheet 2 INVENTOR.

FLOYD D. BURNSIDE APPARATUS AND METHOD FOR FILTERING WELL FLUIDS BACKGROUND OF THE INVENTION 1. Field of the Invention- The invention relates to the working of wells; and, more particularly, to apparatus and method for removing foreign materials from well fluids.

2. Description of the Prior Art In the workover of wells, it is necessary to remove foreign materials, such as solid particles or the like,

from the well fluids standing in a well casing prior to installing artificial lift equipment therein or putting the well in production. Current practice involves the circulation of clean fluids in the well. This circulation tends to agitate trapped solid particles without removing them due to improper removal parameters. Such parameters, for example, may be the size of the particles, the particle-carrying characteristics of the clean fluids being circulated, etc. Other techniques involve the use of downhole pumps equipped with filters; how- SUMMARY OF THE INVENTION It is an object of this invention to provide improved apparatus and method for filtering well fluids standing in the casing of a well borehole.

It is a further object of this invention to provide a method and apparatus for increasing the amount of formation fluids produced from a well borehole over the useful life of workover equipment. It is a still further object to carry out the foregoing objects using an expendable filtering device which can be easily crushed and broken with workover equipment so that it can be removed, if necessary, from the well borehole.

These and other objects are preferably accomplished by extending a screen filter down the casing of a well borehole, the filter having apertures therein of a sufficient size to pass well fluids therethrough while excluding solid particles of a predetermined size. The filter is closed at the top and open at the bottom and is extended into contact with the well fluids thus forcing the fluids up through the filter and out into the well borehole above the filter while trapping the particles therein.

2 BRIEF DESCRIPTION OF THE DRAWING- FIG. 1 is a vertical sectional view of a device for carrying out the techniques of my invention;

FIG. 2 is a vertical sectional view of apparatus in accordance with my invention installed in a well borehole; and p FIGS. 3 through 5 are vertical sectional, partial views of a method for carrying out my invention using the apparatus of FIG. 2. I

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG.'1 of the drawing, a preferred device is shown for carrying out the techniques of over approximately one-eighth of an inch in diameter my invention. Device 10 preferably includes anouter shell 11 having a plurality of apertures therein, such as (or any other size as determined by experience, intended use, and particle size in well fluids).

A closure member, such as a substantially flat cap 15, is disposed at the upper end of the device 10 and is secured to or otherwise integral with outer shell 11. Screen 13 may also be secured to cap 15. In any event, preferably cap 15 closes off at least the upper end of screen 13 and preferably also the upper end of outer shell 11. As will be discussed further hereinbelow, the techniques of my-invention may be carried out using only screen 13 and cap 15 provided that the lower open end 16 of screen 13 forms a substantially fluid-tight seal, albeit temporary, with the wall of a well casing as will also be discussed further hereinbelow.

A flexible casing wall guide member, in the preferred form of a rubber guide shoe 17, is disposed at the bottom of screen 13 and outer shell 11. In the preferred fonn of the invention, guide shoe 17 is secured to or otherwise fastened to shell 11 with the open end 16 of screen 13 extending through substantially the center of guide shoe 17. End 16 may extend a short distance below guide shoe 17; if desired. Further, the maximum diameter of guide shoe 17 is selected so that it is substantially the same as the inside diameter of the well casing it is desired to treat as will be discussed further hereinbelow. The material comprising shoe 17 preferably is firm enough to engage and scrape the wall of the casing as the device 10 is lowered therein; but flexible enough to bend upwardly and permit well fluids to bypass it should the screen 13 (and the annulus 18 formed between screen 13 and outer shell 11) become filled withsolid particles. In that case, the well fluids pass about the flexible fingers 19 of shoe 17 while fingers 19 trap at least some of the larger-sized solid particles in the well fluids. Thus, the device 10 would not be rendered entirely inoperative should it engage a greater volume of solid particles than can be trapped by it. Further, the lowermost portion of shoe 17 is substantially concave as at cavity 20; this cavity 20, together with fingers 19, serves to guide well fluids outwardly from the wall of the well casing, inwardly thereof and up into screen 13 as will be discussed further hereinbelow.

Finally, a plurality of centralizing elements, such as rubber grommet-type centralizers 21 are disposed about the upper end of device 10 for centralizing the device in a well casing. These centralizers serve as wear points for device 10 rather than having outer shell 11 rubbing or knocking against the well casing wall. Thus, each centralizer 21 preferably includes an outer portion cap 22 having a convex surface for engaging the well casing wall. A similar but small cap-type portion 23, connected to cap portion 22 through connector 24, snap-fits on the like into apertures 25 in the wall of outer shell 11. The exact location of centralizers 21 is a matter of choice; however, the greatest diameter of the device, at centralizers 21 which are preferably located on substantially the same horizontal plane, is substantially equal to the inner diameter of the well casing desired to be treated.

Referring now to FIG. 2, a well borehole 26 is shown extending down into a subterranean hydrocarbon-bearing earth formation 27. Borehole 26 is cased, as at casing 28, with casing 28 preferably cemented therein, as at cementing 29. It is to be understood that it is desired to use equipment, such as artificial lift equipment, to produce of fluids from well borehole 26. However, it is first desirable to remove foreign matter from well fluids standing in well casing 28. Thus, in accordance with my invention, tubing means 30 or steel cable or the like is used to push the device down the length of well casing 28. As can be seen in FIG. 2, centralizers 21 serve to centralize the device 10 within casing 28. The resilient fingers 19 of guide shoe 17 engage the inner wall 31 of well casing 28. In FIG. 2 the device 10 is to be understood as being of a preselected length sufficient to trap all of the solid particles present in the well fluids standing in well casing 28. Also, the position of the device 10 in well casing 28 in FIG. 2 is to be understood as not necessarily the initial point of engagement of the device 10 with the well fluids standing in well casing 28.

In operation, the device 10 is forced down within the well casing 28 thus scraping solid particles off the wall 31 and passing well fluids inwardly thereof and up through the screen 13 as can be seen in FIG. 3. Here, portions of the arrangement of FIG. 2 have been omitted for convenience ofillustration.

Solid particles present in the well fluids below device 10 are scraped off of wall 31 of casing 28 by resilient fingers 19. As can be seen by the arrows, the well fluids pass up through screen 13, out slits 14 therein and into annulus l8 trapping solid particles 32 in screen 13. The well fluids then exit through slots 12 in outer shell 11 and pass up into the annulus 33 formed between device 10 and wall 31 and above guide shoe 19.

The downward movement of device 10 is preferably continued until the device 10 reaches the bottom of the well borehole 26 as can be seen in FIG. 4. At this point, the annulus 18 may be partially or substantially totally filled with solid particles. Also, depending on the quantity of solid particles present in the well fluids, the screen 13 may also be partially or substantially totally filled with solid particles as shown in FIG. 4.

Should the quantity of solid particle present in the well fluids standing in well casing 28 be more than can be accommodated by the internal capacity of both annulus 18 and screen 13, the device 10 of my invention would not be rendered entirely inoperative by solid particles bypassing device 10. For example, referring now to FIG. 5, should screen 13 and annulus 18 be substantially filled with solid particles as shown, the'increased pressure on guide shoe 17 would cause resilient fingers 19 to bend upwardly with relatively particle-.

free well fluids bypassing fingers l9 and entering annulus 33 above shoe 17 as indicated by the arrows. Solid particles would remain below shoe 17 and be pushed to the bottom of well borehole 26 by the continued downward movement of device 10.

Preferably, all of the components of device 10 are made of a drillable material, such as cast iron, fiberglass, or heat-resistant plastics. In this manner well borehole 26 may be drilled below the bottom producing zone allowing the device 10 to remain in an unused area, thus rendering the device expendable and it need not, and preferably should not, be recovered from the bottom of the well borehole where it has trapped undesirable solid particles. Also, device 10, may be easily crushed and broken with workover equipment if it is desired to be removed from the wall borehole. As can be seen by the foregoing, only screen 13, closed at its top, and guide shoe 17 or the like, are necessary for carrying out the techniques of my invention. However, preferably, the capacity and efficiency of device 10 is increased by the preferred embodiment described hereinabove.

In summary, an expendable inexpensive well fluids cleaning device has been disclosed which, upon downward motion through well fluids standing in a well borehole, effectively cleans the well fluids of foreign material that often plugs well pumping or natural flow equipment, such as bottom hole pump suctions, artificial lift equipment or small orifices in natural flow equipment. Thus, such workover or equipment problems are solved by the techniques of my invention. That is, those equipment failures associated with the necessity of pumping dirty well casing fluids are alleviated on start-up. Also, the plugging of surface chokes on flowing wells is prevented if such plugging material is the result of workover or completion operations and is contained in the static column of well casing fluids. The amount of fluids produced over the useful life of workover equipment is increased and fouling of gas lift valves caused by solid particles held in static well fluids is prevented. Finally, the techniques of my invention may be used on both new and reworked wells.

I claim as my invention:

1. Apparatus for filtering well fluids standing in the casing of a well borehole comprising:

a screen disposed within and extending longitudinally of said well borehole, said screen having a plurality of apertures therein adapted to pass particle-free well fluids therethrough while excluding particles of a predetermined size in said well fluids from passing through the screen, said screen being open at its lower end;

an outer shell surrounding said screen and extending longitudinally thereof, said shell forming an annulus with said screen and having apertures therein of a size sufficient to pass relatively particle-free well fluids therethrough while excluding particles of a predetermined size;

a casing wall contact means associated with the lower end of said screen for scraping the wall of said well casing as said screen is lowered in said well borehole; and

a substantially imperforate closure member secured to the upper end of said screen and outer shell.

2. The apparatus of claim 1 wherein said casing wall contact means includes flexible fingers thereon having a maximum diameter substantially the same as the inner diameter of said well casing.

3. The apparatus of claim 1 including centralizing means associated with said screen for centralizing said screen within said well casing; and i the open lower end of said screen extending through said casing wall contact means.

4. The apparatus of claim 1 wherein said screen and said closure member are made of a material drillable by a drilling tool.

5. A device for filtering well fluids standing in the casing of a well borehole comprising:

a longitudinally extending inner screen filter;

an outer shell surrounding said screen filter and forming an annulus therebetween;

said filter and said shell having apertures therein of a size sufficient to pass fluids therethrough while excluding particles of a predetermined size.

a substantially imperforate closure member closing the top of both said filter and said shell; and

resilient well casing wall contact means closing the lower end of said shell but having the open lower end of said screen filter extending therethrough, said contact means having a maximum diameter substantially equal to the inner diameter of said well casing.

6. The device of claim 5 including centralizing means associated with said shell for centralizing said device in said well borehole.

7. The device of claim 5 wherein all of said filter, said shell, said closure member and said contact means are made of drillable material. 

1. Apparatus for filtering well fluids standing in the casing of a well borehole comprising: a screen disposed within and extending longitudinally of said well borehole, said screen having a plurality of apertures therein adapted to pass particle-free well fluids therethrough while excluding particles of a predetermined size in said well fluids from passing through the screen, said screen being open at its lower end; an outer shell surrounding said screen and extending longitudinally thereof, said shell forming an annulus with said screen and having apertures therein of a size sufficient to pass relatively particle-free well fluids therethrough while excluding particles of a predetermined size; a casing wall contact means associated with the lower end of said screen for scraping the wall of said well casing as said screen is lowered in said well borehole; and a substantially imperforate closure member secured to the upper end of said screen and outer shell.
 2. The apparatus of claim 1 wherein said casing wall contact means includes flexible fingers thereon having a maximum diameter substantially the same as the inner diameter of said well casing.
 3. The apparatus of claim 1 including centralizing means associated with said screen for centralizing said screen within said well casing; and the open lower end of said screen extending through said casing wall contact means.
 4. The apparatus of claim 1 wherein said screen and said closure member are made of a material drillable by a drilling tool.
 5. A device for filtering well fluids standing in the casing of a well borehole comprising: a longitudinally extending inner screen filter; an outer shell surrounding said screen filter and forming an annulus therebetween; said filter and said shell having apertures therein of a size sufficient to pass fluids therethrough while excluding particles of a predetermined size. a substantially imperforate closure member closing the top of both said filter and said shell; and resilient well casing wall contact means closing the lower end of said shell but having the open lower end of said screen filter extending therethrough, said contact means having a maximum diameter substantially equal to the inner diameter of said well casing.
 6. The device of claim 5 including centralizing means associated with said shell for centralizing said device in said well borehole.
 7. The device of claim 5 wherein all of said filter, said shell, said closure member and said contact means are made of drillable material. 